Effects of Sample Pretreatment and Contamination on Bivalve Shell and Carrara Marble δ18O and δ13C Signatures
Stable isotope signatures of bivalve shells serve as important proxies of past environmental conditions. However, such data can be biased as a consequence of physical and chemical pretreatment and contamination during sampling. To systematically assess these issues, homogenized aragonitic shell powder, as well as Carrara marble powder (calcite) were exposed to ultrasound, a set of different staining solutions and cleaning agents that are typically employed in bivalve sclerochronology. Furthermore, these materials were artificially contaminated with periostracum, Alcian Blue and cured adhesives. Whereas some treatments had no effects, severe isotope shifts were observed after immersion in Feigl’s solution or contamination with certain epoxies. The majority of tested treatments conducted with the carbonate powders and contaminants added to them caused only minor to moderate isotope offsets. In conclusion, pretreatment of bivalve shells with an intended use for isotope analysis should be kept at an absolute minimum and contamination with adhesives etc. should be avoided. Specimens from museum collections may be of limited value for isotope studies, unless the history of sample treatment is known. Although only a few of the tested substances and methods strongly biased the isotope signatures, even small changes can accumulate to levels that are inacceptable for environmental reconstructions.
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Effects of Sample Pretreatment and Contamination on Bivalve Shell and Carrara Marble δ18O and δ13C Signatures. Bernd R. Schöne, Katharina Schmitt. Presented at The 81st Annual Meeting of the Society for American Archaeology, Vancouver, British Columbia. 2017 ( tDAR id: 431186)
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Abstract Id(s): 14675